Thermoplastic elastomers are soft materials having rubber elasticity, do not require a vulcanization process and can be molded and recycled as in thermoplastic resins. They have been frequently used in the fields of, for example, automobile parts, home-appliance parts, wire coating, medical parts, sundry goods, and footgear. Among these thermoplastic elastomers, certain proposals have been made on elastomer compositions using a hydrogenated product of a block copolymer (hereinafter may briefly referred to as “hydrogenated block copolymer”) having a polymer block comprising an aromatic vinyl compound and a polymer block comprising a conjugated diene compound. For example, Japanese Unexamined Patent Application Publication (JP-A) No. 59-131613, JP-A No. 08-225713, JP-A No. 2000-109640, and PCT International Publication No. WO 95/00566 propose techniques in which an elastomer composition comprising a hydrogenated block copolymer with, for example, a hydrocarbon oil and an olefin polymer is crosslinked using a crosslinking agent such as an organic peroxide and a coagent to thereby improve rubber elasticity (compression set) at high temperatures of the resulting elastomer composition.
The elastomer composition comprising the hydrogenated block copolymer can be recycled, which is a feature of such thermoplastic elastomers. However, the elastomer composition is crosslinked only in its soft segment comprising the conjugated diene compound block of the hydrogenated block copolymer, therefore has insufficient rubber elasticity at 100° C. or higher and does not achieve a low compression set level at high temperatures. Such a low compression set at high temperatures can be achieved by the use of a vulcanized rubber. This is because when the temperature of a test for determining the compression set reaches the glass transition point (Tg) of the vinyl aromatic block or higher, the polymer block comprising the vinyl aromatic compound has decreased constraint force, and a hard segment including the polymer block comprising the aromatic vinyl compound becomes less contributory to rubber elasticity.
Accordingly, an object of the present invention is to provide a thermoplastic elastomer composition which contains an addition block copolymer and a polyolefin, has excellent strain recovery at high temperatures, is flexible and has satisfactory rubber properties, a production process therefor, a molded article comprising the thermoplastic elastomer composition, and a specific addition block copolymer constituting the thermoplastic elastomer composition.